Aluminum Toxicity and DNA Synthesis in Wheat Roots¹

Abstract

Aluminum toxicity is a deterrant to the growth of plants in acid soil. Little is known of the initial site or sites of AI injury in plant roots nor of the sequence of events that characterize AI toxicity. The objective of this study was to document some effects of short-term exposure to AI in two wheat (Triticum aestivum L.) cultivars, Eagle and Atlas 66. Root elongation in Eagle was much more susceptible to concentrations of 0.02 to 1.85 mM AI than was root elongation in Atlas 66. A 2-h exposure to 0.19 mM AI drastically inhibited root elongation in Eagle, whereas a 48-h treatment with 0.19 mM AI had little effect on root elongation in Atlas 66. Exposures of Eagle seedlings to 0.19 mM AI for 4 h caused a 32% inhibition in subsequent incorporation of 3 H-thymidine into DNA, with the degree of inhibition increasing with duration of exposure to AI. In Atlas 66, there was a 10% reduction in incorporation of radioactivity into the DNA fraction for all the AI pretreatments, ranging from 2 to 48 h. Exposure of Eagle roots to AI for 2 h showed this same 10% reduction in incorporation of radioactivity into DNA. For both cultivars, there usually was a 10 to 20% decrease in 3 H-thymidine uptake by whole roots after 0.19 mM AI pretreatment periods of 2 to 12 h as compared with control plants not receiving AI. The extent of inhibition was fairly constant and was not correlated with duration of AI pretreatment for either cultivar. There was a similar depression of 3 Mthymidine uptake in root tips of Eagle after 4 to 12 h of AI pretreatment. The reduction of 3 H-thymidine uptake in both cultivars resembled the depression of 3 H-thymidine incorporation into DNA in Atlas 66 but not in Eagle. This work suggests that AI has two effects on susceptible cultivars: a rapid inhibition of root elongation followed by an inhibition of DNA synthesis. Another effect of AI on both the tolerant and the susceptible cultivar, that of depression of 3 H-thymidine uptake, also was seen.

Determination of critical pH and Al concentration of acidic Ultisols for wheat and canola crops

“…The plant root system is affected by high Al concentrations because Al interferes with the uptake, transport, and utilization of essential plant nutrients such as P, K, Ca, Mg, and water, as well as enzyme activity in the roots (Lofton et al, 2010). Wallace and Anderson (1984) reported that DNA synthesis in plant roots was inhibited by Al and was followed by root elongation. Due to the lower cation exchange capacity and higher Al content of the Ultisol from Hunan, compared with the Ultisol from Anhui at the same soil pH, the threshold soil pH differed and was higher for the Ultisol from Hunan.…”

Metabolic alterations proposed by proteome in rice roots grown under low P and high Al concentration under low pH

“…DNA damage is a well known phenomenon of Al toxicity [46][47][48]. Matsumoto [49] proposed that DNA-Al complex formation and repression of transcription by Al could be a …”

INFLUENCE OF ALUMINUM ON MINERAL NUTRIENT UPTAKE AND ACCUMULATION INURTICA PILULIFERAL.

“…Al can inhibit the uptake of potassium (K + ) (Liu and Luan, 2001), calcium (Ca 2+ ) (Huang et al, 1992), and magnesium (Mg 2+ ) (Keltjens, 1995), and interacts with both microtubules and actin filaments leading to deleterious effects on cytoskeletal dynamics (Blancaflor et al, 1998;Sivaguru et al, 1999Sivaguru et al, , 2000Silva et al, 2000). Aluminum modifies composition, physical properties, and structure of the cell wall and plasma membrane (Wagatsuma et al, 1995;Zhang et al, 1997;Ishikawa and Wagatsuma, 1998) and affects phosphate and/or nucleotide metabolism (Matsumoto and Morimura, 1980;Wallace and Anderson, 1984). Aluminum interference with the signal transduction pathway could also play a role in Al toxicity (Jones and Kochian, 1995;Jones et al, 1998;Ramos-Diaz et al, 2007).…”